1. Field of the Invention
The present invention relates to a moving vehicle steering circuit system capable of both automatic and manual steering.
2. Description of the Related Art
A conventional steering circuit system for a moving vehicle is known in which pressurized oil discharged from a hydraulic pump is fed to a steering cylinder by a manual operation steering valve. It is also known that a pilot operation check valve may be provided for the purpose of preventing the pressurized oil of the steering cylinder from flowing back. This ensures the function of a return side or drain line by utilizing the pilot pressure as long as the pressurized oil is fed to one side of the steering cylinder.
However, such steering circuit systems inconveniently require manual operation by an operator, and thus automatic operation cannot be achieved. When the pressurized oil ceases to be fed to the steering cylinder, the pressurized oil of the return side line is suddenly blocked. Nevertheless, since the steering wheel has inertia, it is vibrated by the oil hammer and the stability of the vehicle body is adversely affected.